Liquid crystal display (“LCD”) devices have been regarded as next generation display devices by providing increased value because of their low power consumption and high portability. An LCD device is driven based on optical anisotropy and polarization characteristics of a liquid crystal material. In general, an LCD device includes two substrates, which are spaced apart and facing each other, and a liquid crystal layer interposed between the two substrates. Each of the substrates includes an electrode. The electrodes from respective substrates face one the other. An electric field is induced between the electrodes by applying a voltage to each electrode. An alignment direction of the liquid crystal molecules changes in accordance with a variation in the intensity or the direction of the electric field. The LCD device displays a picture by varying light transmittance according to the arrangement of the liquid crystal molecules.
Generally, the LCD device is manufactured by fabricating an array substrate including a thin film transistor and a pixel electrode, fabricating a color filter substrate including a color filter and a common electrode, and interposing a liquid crystal layer between the array substrate and the color filter substrate. In addition, active matrix liquid crystal display (“AMLCD”) devices, which include thin film transistors as switching devices for a plurality of pixels, have been widely used due to their high resolution and ability to display fast moving images.
FIG. 1 is a three-dimensional view of part of an LCD device according to the related art and illustrates an active area where liquid crystal molecules are driven. In FIG. 1, the LCD device 1 includes upper and lower substrates 60 and 10 spaced apart from and facing each other and a liquid crystal layer 80 interposed between the upper substrate 60 and the lower substrate 10. A plurality of gate lines 8 and a plurality of data lines 20 are formed on an inner surface of the lower substrate 60. The gate lines 8 and the data lines 20 cross each other to define pixel regions, each of which serves as a sub-pixel SP. A thin film transistor (“TFT”) T is formed as a switching element at each crossing of the gate lines 8 and the data lines 20. A pixel electrode 30, which is connected to the thin film transistor T, is formed in each sub-pixel SP.
A color filter layer 70 and a common electrode 75 are sequentially formed on an inner surface of the upper substrate 60 facing the lower substrate 10. The color filter layer 70 includes red, green and blue color filter patterns, which correspond to the sub-pixels SP, respectively, and are sequentially arranged. Although not shown in the figure, a black matrix is formed between adjacent color filter patterns to block light in a region where an arrangement of liquid crystal molecules of the liquid crystal layer 80 are not controlled.
FIG. 2 is a schematic plan view of an LCD device according to the related art. In FIG. 2, gate lines, data lines and a color filter layer are schematically illustrated, and a black matrix and thin film transistors are not shown. As illustrated in FIG. 2, in the LCD device 1, gate lines 8 and data lines 20 cross each other to define pixel regions, each of which acts as a sub-pixel SP. Red, green and blue color filter patterns R, G and B are sequentially and repeatedly arranged. The red, green and blue color filter patterns R, G and B correspond to the sub-pixels SP, respectively. The red, green and blue sub-pixels RSP, GSP and BSP constitute a pixel P. However, in the LCD device 1 having three sub-pixels RSP, GSP and BSP as the pixel P, light emitted from a backlight, which is disposed at a rear side of a lower substrate including the gate and data lines 8 and 20 thereon, transmits the red, green and blue color filter patterns R, G and B to thereby produce color images. Thus, brightness of the LCD device is lowered.
To improve the brightness, another LCD device having four sub-pixels of red, green, blue and white as one pixel may be used. A white sub-pixel includes a colorless, transparent pattern. Hereinafter, the colorless, transparent pattern may be referred to as a white color filter pattern. FIG. 3 is a schematic plan view of an LCD device having four color filter patterns according to the related art. As in FIG. 2, a black matrix and thin film transistors are not shown.
As illustrated in FIG. 3, the LCD device 85 includes red, green, blue and white color filter patterns. The red, green, blue and white color filter patterns are formed in sub-pixels SP, respectively, and red, green, blue and white sub-pixels RSP, GSP, BSP and WSP constitute a pixel P. In one embodiment, the red, green, blue and white sub-pixels RSP, GSP, BSP and WSP have a rectangular shape and are similar in size. In an alternate embodiment, the sub-pixels may have a different shape or may differ in size. In the LCD device 85 having the red, green, blue and white color filter patterns, substantially all of light passing through the white sub-pixel WSP is transmitted from the backlight through the white color filter pattern W, and the brightness is thus increased. However, since the white sub-pixel WSP is 25% of the pixel P, the sizes of the red, green and blue sub-pixels RSP, GSP and BSP in the active area are decreased. In other words, the area that the white sub-pixel WSP is covering on the pixel P is less area available for each of the other sub-pixels, RSP, GSP and BSP. Therefore, although the brightness is increased, color purity is lowered. In addition, the difference of a contrast ratio between a gray level and a white level is deteriorated due to the increased white brightness, and thus image qualities are decreased.